Analysis St. 17: The top of the Col du Tourmalet stands at 6939 feet above sea level and the start of the climb sits at 2329 feet, meaning today’s final ascent gained 4610 vertical feet in 11.5 miles. If you count the climb from the town of Adast (which sits at 1542 feet) to the official start of the climb, the riders climbed more than a vertical mile (5397 feet) in the final 20 miles of Stage 17. Guess what – it can be hard to breathe up there.

- By Chris Carmichael –

Once the riders get above about 5000 feet above sea level, they start to be affected by altitude. And by the time they approach nearly 7,000 feet above sea level, their performance can be significantly impacted. Did the elevation play a role in the stalemate between Andy Schleck and Alberto Contador today on the Col du Tourmalet?

Elevations from 5,000 to 7,000 feet above sea level are referred to as moderate altitude, meaning it’s high enough for sedentary people and athletes to experience some physiological effects of the thinner air, but not so high that the altitude is dangerous or requires any special equipment. In fact, many reasonably fit people barely notice the difference between walking around at sea level and between 5,000-7,000 feet. When you’re more active, like going for a bike ride, you notice the altitude, but at moderate elevations even that impact is not that great. For elite cyclists, the elevation at top of the Col du Tourmalet is not high enough to cause them much problem at all, unless they are in the Tour de France and trying to ride at maximum power.

Was today’s result influenced by altitude? Yes and no. The rider’s power outputs in the final 3-4 kilometers of the stage may have been up to 10% lower than what those same riders could have produced with a similar effort at sea level. We see this decline in maximum sustainable power output when riders perform lab tests at sea level and then again in Colorado Springs at 6200 feet above sea level. But due to the weather conditions, the fact we’re in the third week of the Tour de France, and that the riders reached the Tourmalet after more than 4 hours and two major climbs, it would be difficult to determine exactly how much impact altitude had on any individual riders performance today.

And each athlete responds differently to altitude, so the decline in power due to altitude for one rider could be 3% and for another rider it could 8%. That alone can give one athlete an advantage when races get into the high mountains, but that advantage gets even greater when the attacks start flying. Attacks push riders well above lactate threshold, and riders who cope with altitude better are able to process that lactate more quickly at higher elevations. That means they can sustain strong attacks for longer distances, and they can recover more quickly after major efforts.

But since no athlete is completely unaffected by altitude when racing above 5,000 feet in elevation, you can begin to understand why we didn’t see a large number of vicious attacks by either Andy Schleck or Alberto Contador in the final kilometers of the Tourmalet. The higher you get on the mountain, the more costly every attack and surge becomes. Just maintaining a high pace gets more difficult as well, so riders sometimes don’t feel as willing or able to attack. And if you push yourself over the limit at altitude, you crack more spectacularly than you would at a lower elevation. As a result, the risks of launching multiple attacks increases greatly, because if you crack in that thin air you won’t just lose contact with your rival’s wheel, you’ll just about come to a dead stop before you can recover enough to return to a reasonable speed.

By the time Andy Schleck and Alberto Contador reached the final three kilometers of Stage 17 – and this goes for all the riders behind them as well – there wasn’t much else for them to do but maintain as high a steady pace as they could. At the intensity they were holding, and at that altitude, you only have the potential for one or two big accelerations, and pulling the trigger on those efforts could just as easy backfire on you and push you over your limit. So don’t mistake what you saw in the closing kilometers of the Tourmalet today for a passive ride to the summit; it becomes increasingly difficult for racers who spend very little time competing at elevations above 5,000 feet to launch searing attacks on the upper slopes of the high mountains.

• Chris Carmichael is Founder and CEO of Carmichael Training Systems and coach to Lance Armstrong. In 2010, CTS is celebrating its 10th Anniversary of being the premier destination for coaching, camps, and performance testing. For information on what CTS can do for your performance, visit www.trainright.com, call 866-355-0645, or find us on Facebook at www.facebook.com/carmichaeltrainingsystems.